Merced River and Yosemite Falls.
Spring in Yosemite Valley. Dogwood in bloom, waterfalls in their full splendor and a battle between two environmental groups. The Wilderness Society and Friends of Yosemite don't see eye to eye over the recent 9th District Court's decision to halt the restoration and flood recovery plans in Yosemite.Maloney / CHRONICLE less

Merced River and Yosemite Falls.
Spring in Yosemite Valley. Dogwood in bloom, waterfalls in their full splendor and a battle between two environmental groups. The Wilderness Society and Friends of Yosemite ... more

Photo: Michael Maloney

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Joseph Grinnell skins a speciman in a field tent, circa 1922. THE BANCROFT LIBRARY, UNIVERSITY OF CALIFORNIA, BERKELEY

Joseph Grinnell skins a speciman in a field tent, circa 1922. THE BANCROFT LIBRARY, UNIVERSITY OF CALIFORNIA, BERKELEY

Photo: Michelle Nijhus

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Photo: MICHELLE NIJHUIS

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close up of skull, possibly of a marten

close up of skull, possibly of a marten

Photo: Michelle Nijhuis

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Global warming stalks Yosemite / Retracing the steps of a meticulous early 20th century biologist, researchers find that some of the parks tiniest residents have moved a startling distance uphill

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Biologist Joseph Grinnell was a world-class researcher, but he wasn't always the most pleasant of traveling companions. "We'd be sitting in camp, and we'd both be skinning," recalled naturalist Ward Russell, who spent years helping Grinnell trap, skin and otherwise document the wildlife of California. "Pretty soon, he'd throw a rat over to me, and he'd say, 'Here, Russell, finish this one up,' and he'd just ... pick up his notebook, and start writing."

Despite his dubious camp etiquette, Grinnell's devoted record-keeping led to one of the most famous datasets in modern biology. During their travels throughout California between 1904 and the late 1930s, Grinnell and his colleagues snared or shot more than 20,000 mammal, bird, reptile and amphibian specimens, took about 2,000 photographs, and filled 13,000 journal pages with erratic penmanship and beautifully detailed observations. Their portrait of the natural diversity of California remains unmatched in its scope and depth.

Grinnell, the founding director of the Museum of Vertebrate Zoology at UC Berkeley, was by all accounts a dedicated, methodical researcher. His field journal, which he kept until just five days before his death in 1939, numbered more than 3,000 pages. He helped build the museum's store of animal skins and skeletons, an international collection now ranging from a hippo skull the size of an easy chair to shrew skeletons no larger than a thumb. His theories about species and their habitats are still taught in college biology courses.

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Yet in 1910, Grinnell predicted that the real value of his and his colleagues' painstaking fieldwork would not "be realized until the lapse of many years, possibly a century." Change was clearly part of the natural world, he wrote. But he also saw "vastly more conspicuous" transformations of the environment in the speedy deforestation, cultivation and irrigation of the West. He believed that in the future, scientists would return to some of his more than 700 study sites, and use his findings to chart these changes.

That future is now. Though several researchers have mined the Grinnell data during the past nine decades, no one has ever attempted a broad resurvey of the sites. Now, researchers at the Museum of Vertebrate Zoology, inspired by Grinnell's writings, hope to revisit about a third of the California sites by the museum's centennial in 2008. With funding from the U.S. Geological Survey and the Yosemite Fund, a nonprofit organization that supports research in the park, biologists began in 2003 to study 40 sites along Grinnell's "Yosemite Transect."

Just as Grinnell foresaw, his data provide evidence of conspicuous change in the natural world. But even the prescient Joseph Grinnell didn't count on global warming.

During a driving rainstorm in mid-August, near the head of a long, gently sloping glacial valley called Lyell Canyon, the soggy modern-day Grinnell team takes temporary shelter in camp. Berkeley professor
James Patton
, his wife, Carol, and U.S. Geological Survey wildlife biologist
Les Chow
have spent much of the summer here, among the toothy granite peaks of Yosemite National Park, following the very precise footsteps of Joseph Grinnell and his colleagues.

Each day, they check long rows of mammal traps, hiking through alpine meadows and up rocky slopes. Patton skins a few unlucky specimens with a small pair of scissors, then records his findings and observations using the exacting Grinnell method. Patton even stores his trays of animal skins in the same scuffed crates once used by Grinnell and his colleagues; the wooden boxes, originally designed to carry cans of lard, have survived a century of nearly constant use.

For Patton, who has spent his career studying small mammals throughout the Americas, the project is also a journey into his scientific heritage. Grinnell and his colleagues often wrote down their musings about the natural world, and Patton sometimes dips into their journals during his days in the field. Their voluminous notebook entries, with their imperfections, their detours, and their moments of clarity, exude the excitement of discovery.

"To be at the same spot, the same rock outcrop, and to be able to read what they were seeing and thinking ..." Patton shakes his head. "The only reason we have this opportunity is that Grinnell was fanatic about what he did."

Field science has changed a bit since the days of Grinnell. In the Lyell Canyon camp, the researchers eat rehydrated dinners out of foil packets instead of cooking on an open fire, and eschew worsted wool in favor of Gore-Tex.

Some researchers store their field journals on Palm Pilots, instead of in the traditional lined loose-leaf notebooks. And while Grinnell used stacks of "museum specials," a sort of burly mousetrap, to break the backs of tens of thousands of small mammals, Patton and his crew now trap their subjects alive in slim aluminum boxes, often releasing them unhurt.

But the most significant difference between the old and new Grinnell expeditions lies inside the traps. When Patton first visited Lyell Canyon in 2003, he opened one of his aluminum boxes to find a small mouse with remarkably large ears. "I thought, 'What the heck is this thing doing here?' " says Patton. "I was dumbfounded." Its huge ears immediately introduced it as a piñon mouse, which, as its name suggests, is a familiar resident of the lower-elevation piñon pine forests of the Sierra Nevada.

On the east side of the Sierra, Grinnell and his assistants only saw piñon mice below 7,000 feet, a finding confirmed by other researchers throughout the central part of the range. Patton's group found numerous mice frolicking in the talus slopes of Lyell Canyon, 10,200 feet above sea level and about eight miles from the nearest Grinnell sighting. The distance was too great to be the work of just a few wandering individuals; it was clear to Patton that the range of the piñon mouse, and its habitat, were far different now than in 1915.

"They're common, and they're easily identified," says Patton. "If they had been up here before, (Grinnell and his compatriots) would have seen them."

The new Yosemite crew has uncovered more changes. Four other small mammals have expanded their turf in the park, increasing the upper limits of their ranges by an average of 2,000 vertical feet.

The alpine chipmunk, two high-elevation ground squirrels -- including the Belding's ground squirrel, known as the "picket pin" for its ramrod-straight alarm posture -- and a small relative of the rabbit called the pika have retracted their haunts uphill, drawing in the lower edge of their ranges by an average of 1,700 vertical feet. At least two species of small mammals, a chipmunk and a wood rat, have dramatically shrunk the overall size of their ranges, and are now extremely rare in the park.

Ornithologist Andrew Rush, who recently revisited the Grinnell sites in Yosemite, also saw and heard some surprises. In Lyell Canyon alone, he recorded 17 bird species not mentioned by the Grinnell team, many of them riparian and wetland species more familiar at lower elevations. Some of these species, such as the blue-winged teal and the mallard, were even breeding in the canyon's high-elevation meadows.

The Grinnell survey and resurvey represent just two snapshots in time, and what happened in the intervening years is largely unknown. But studies of particular species in the area help fill in the gaps, and confirm that neither Grinnell nor his modern followers witnessed a fleeting anomaly.

So what's going on in Yosemite? Fire suppression, with its transforming effects on habitat, has certainly played a part in the rearrangements of wildlife at lower elevations. It may also explain why a couple of small mammal species moved downhill in the park, defying the overall trend. Yet in alpine areas such as Lyell Canyon, Grinnell photographs from 1915 show that forests and meadows looked almost the same as they do today.

There is little question, however, that the entire park is warmer than it was during Grinnell's time. Snow is melting earlier in the spring, and Lyell Glacier, like other glaciers throughout the Sierra, is disappearing. Researchers at Portland State University in Oregon found, using another series of historical photographs, that the surface area of the western lobe of Lyell has shrunk 30 percent since 1883, and the eastern lobe has contracted 70 percent.

Weather records from Yosemite Valley show a 9 degree Fahrenheit increase in mean minimum temperatures over the past century. Though weather data from higher elevations are spotty, Museum of Vertebrate Zoology researcher Robert Hijmans estimates that mean minimum temperatures throughout the central Sierra rose 5 degrees Fahrenheit over the last 100 years.

The vast majority of scientists say humans have a lot to do with such changes, which are now observed around the world. They say the rising concentration of carbon dioxide and other greenhouse gases in our atmosphere -- due in large part to cars, coal-fired power plants and other human inventions -- bears significant blame for the planet's warming climate.

In high, relatively undisturbed places such as Lyell Canyon, these rising temperatures -- and their various effects on the landscape -- are the most dramatic changes in the environment over the past century, and they are the most obvious explanation for the shifting alpine wildlife of Yosemite.

For some species, it appears, just a few degrees' difference in temperature makes home uncomfortable and previously inhospitable habitat more welcoming. "For the pika, the alpine chipmunk and the Belding's ground squirrel, I don't know what else to link it to, other than climate change," says Patton.

Back at the Museum of Vertebrate Zoology, museum director Craig Moritz agrees. "This is a work in progress," he cautions, "but my gut feeling is that we've got a whopping climate change signature."

Thus the legacy of Joseph Grinnell survives, informing a new world. "Grinnell was one of those classic early ecologists that snobby scientists, toward the end of the 20th century, would dismiss as 'descriptive,' " says Raphael Sagarin, a researcher at UCLA who uses historical datasets to study the effects of climate change. "Now we are seeing how important good descriptions of nature really are."

The results of the Grinnell resurvey reflect a much larger pattern, one already documented by legions of scientists. Camille Parmesan, a biologist at the University of Texas at Austin, estimates that researchers have now collected good data on the effects of climate change on more than 1,500 animal and plant species worldwide. Half those species have clearly shifted upward or northward in recent decades, and two-thirds are breeding earlier in the year. Only a handful are moving to warmer climates, or breeding later.

Stanford University biologist Terry Root, who reviewed the existing research in a 2003 paper in the journal Nature, reported that a consistent "fingerprint" of global warming is now perceptible on species "ranging from mollusks to mammals and from grasses to trees."

Scientists warn that even if we could quit adding greenhouse gases to the atmosphere tomorrow, the planet would continue to warm up. Researchers at the National Center for Atmospheric Research in Boulder, Colo., call it the "climate change commitment." What we've already pumped into the atmosphere will cause global air temperatures and sea levels to rise, slowly but significantly, over the next several centuries. Every day of new emissions commits us to yet more warming, and deeper waters.

The Intergovernmental Panel on Climate Change, considered the global scientific authority on the subject, foresees that between 1990 and 2100, Earth's average surface temperature will increase by between 2.5 and 10.4 degrees Fahrenheit. "The projected rate of warming," the panel concluded in its most recent report, "is much larger than the observed changes during the 20th century, and is very likely to be without precedent during at least the last 10,000 years."

Yosemite National Park, like all national parks, is supposed to muffle these and other "vastly more conspicuous" transformations wrought by humans, to use Joseph Grinnell's expression. "It would seem to me that national parks should comprise pieces of the country in which natural conditions are left altogether undisturbed by man," Grinnell wrote to Yosemite Superintendent W.B. Lewis in 1920. Yet the Grinnell resurvey team has found that when it comes to global warming, Yosemite is no refuge.

"Places like Yosemite mean so much to so many people," Patton reflects. "People think we've preserved this piece of the environment, but we haven't. The high-elevation species, those that seem to be retracting upwards, have no place to go -- so when they go, they're gone, and they're never coming back."